>From b3467c27c31ca2034f67f56438cfc8576c8f38b2 Mon Sep 17 00:00:00 2001
From: Paul Eggert <address@hidden>
Date: Sun, 9 Oct 2016 11:29:50 -0700
Subject: [PATCH 2/2] electric-quote-chars fixups
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* lisp/electric.el (electric-quote-chars): Check types and safety
more carefully.
(electric--insertable-p): Don’t bother with string argument, as
that is no longer used.  Don’t call ‘string’ unless needed.
(electric-quote-post-self-insert-function): Use more-mnemonic locals.
Omit no-longer-necessary runtime error diagnostic.
---
 lisp/electric.el | 64 +++++++++++++++++++++++++++++---------------------------
 1 file changed, 33 insertions(+), 31 deletions(-)

diff --git a/lisp/electric.el b/lisp/electric.el
index 5c7be35..b15e8ab 100644
--- a/lisp/electric.el
+++ b/lisp/electric.el
@@ -427,24 +427,27 @@ electric-quote-string
 
 (defcustom electric-quote-chars '(?‘ ?’ ?“ ?”)
   "Curved quote characters for `electric-quote-mode'.
-The items correspond to the left single quote, the right single
-quote, the left double quote, and the right double quote, respectively."
-  :version "25.1"
-  :type 'list :safe 'listp :group 'electricity)
+This list's members correspond to left single quote, right single
+quote, left double quote, and right double quote, respectively."
+  :version "26.1"
+  :type '(list character character character character)
+  :safe #'(lambda (x)
+            (pcase x
+              (`(,(pred characterp) ,(pred characterp)
+		 ,(pred characterp) ,(pred characterp))
+               t)))
+  :group 'electricity)
 
 (defcustom electric-quote-paragraph t
   "Non-nil means to use electric quoting in text paragraphs."
   :version "25.1"
   :type 'boolean :safe 'booleanp :group 'electricity)
 
-(defun electric--insertable-p (string-or-char)
-  (let ((str (if (characterp string-or-char)
-                 (string string-or-char)
-               string-or-char)))
-    (or (not buffer-file-coding-system)
-        (eq (coding-system-base buffer-file-coding-system) 'undecided)
-        (not (unencodable-char-position nil nil buffer-file-coding-system
-                                        nil str)))))
+(defun electric--insertable-p (char)
+  (or (not buffer-file-coding-system)
+      (eq (coding-system-base buffer-file-coding-system) 'undecided)
+      (not (unencodable-char-position nil nil buffer-file-coding-system
+                                      nil (string char)))))
 
 (defun electric-quote-post-self-insert-function ()
   "Function that `electric-quote-mode' adds to `post-self-insert-hook'.
@@ -468,32 +471,31 @@ electric-quote-post-self-insert-function
                   (or (eq last-command-event ?\`)
                       (save-excursion (backward-paragraph) (point)))))))
       (pcase electric-quote-chars
-        (`(,q1 ,q2 ,q3 ,q4)
+        (`(,l ,r ,ll ,rr)
          (when start
            (save-excursion
              (if (eq last-command-event ?\`)
-                 (cond ((and (electric--insertable-p q3)
-                             (search-backward (string q1 ?`) (- (point) 2) t))
-                        (replace-match (string q3))
+                 (cond ((and (electric--insertable-p ll)
+                             (search-backward (string l ?`) (- (point) 2) t))
+                        (replace-match (string ll))
                         (when (and electric-pair-mode
                                    (eq (cdr-safe
-                                        (assq q1 electric-pair-text-pairs))
+                                        (assq l electric-pair-text-pairs))
                                        (char-after)))
                           (delete-char 1))
-                        (setq last-command-event q3))
-                       ((and (electric--insertable-p q1)
+                        (setq last-command-event ll))
+                       ((and (electric--insertable-p l)
                              (search-backward "`" (1- (point)) t))
-                        (replace-match (string q1))
-                        (setq last-command-event q1)))
-               (cond ((and (electric--insertable-p q4)
-                           (search-backward (string q2 ?') (- (point) 2) t))
-                      (replace-match (string q4))
-                      (setq last-command-event q4))
-                     ((and (electric--insertable-p q2)
+                        (replace-match (string l))
+                        (setq last-command-event l)))
+               (cond ((and (electric--insertable-p rr)
+                           (search-backward (string r ?') (- (point) 2) t))
+                      (replace-match (string rr))
+                      (setq last-command-event rr))
+                     ((and (electric--insertable-p r)
                            (search-backward "'" (1- (point)) t))
-                      (replace-match (string q2))
-                      (setq last-command-event q2)))))))
-        (_ (error "‘electric-quote-chars’ must contain exactly 4 characters."))))))
+                      (replace-match (string r))
+                      (setq last-command-event r)))))))))))
 
 (put 'electric-quote-post-self-insert-function 'priority 10)
 
@@ -510,8 +512,8 @@ electric-quote-mode
 `electric-quote-comment', `electric-quote-string', and
 `electric-quote-paragraph'.
 
-Customize `electric-quote-chars' in order to use quote chars
-other than the ones listed here.
+Customize `electric-quote-chars' to use characters other than the
+ones listed here.
 
 This is a global minor mode.  To toggle the mode in a single buffer,
 use `electric-quote-local-mode'."
-- 
2.7.4